Brushless direct current motors, also referred to as BLDC motors, are used in numerous applications nowadays. By way of example, they are used in motor vehicles to support the steering. This constitutes for example a particularly safety-critical function in which, therefore, measures are typically implemented in order to identify possible error states of the brushless direct current motor in a timely manner and to avoid an uncontrolled reaction of the vehicle. In accordance with the prior art, this is carried out for example with the aid of a current measurement in one or a plurality of phases of the brushless direct current motor, or with the aid of a voltage measurement. In particular, it is thus possible to determine a respective current direction of phase currents of the brushless direct current motor and in particular the zero crossings thereof with high accuracy.
Specific disadvantages occur, however, in the case of the variants for determining error states that are known from the prior art. A current measurement is associated in particular with high costs for a measuring circuit necessary for that purpose and yields only a low signal quality in particular at low current intensity. The voltage measurement enables only little meaningfulness regarding the level of the current intensity, requires algorithms that are intensive in respect of computational time and memory space, does not allow monitoring with the motor at a standstill and has a long error identification time at low rotational speed since a plurality of complete electrical revolutions are required in this case.